Are you getting the test code from an e-mail, or cutting and pasting from the verbatim block on Savannah? The verbatim block in the bug report has lines that are longer than 80 characters. In the samples you ran it appears that Matlab is seeing only 80 characters at a time followed by a newline which is leading to bad input messages.

Parenthesized subexpressions create tokens. If the subexpression matches an empty string, an empty string should be returned. Now they just disappear: If I have an expression with two parenthesized subexpressions and the first match empty, only the second token is returned. This is inconsistent with other regex implementations like perl and MATLAB.